1. Field of Invention
The present invention relates to a display device provided with a screen displaying characters, still images, moving images or the like, and also relates to a technique for improving visibility of a display screen in a wide variety of usage environments.
2. Description of the Related Art
A variety of electric appliances with a display screen structured by a liquid crystal panel, including a cell-phone, are prevalent. A liquid crystal panel has characteristics of being thin and light, and mobile laptop personal computers provided with a liquid crystal panel are produced. Furthermore, terminal devices called PDA (Personal Digital Assistant) are produced in large numbers, and becoming common.
As for display panels used in this way, not limited to a liquid crystal panel, the visual image quality is regarded as important, and panels provided with a function of adjusting the brightness and contrast automatically or manually are widely prevalent. For example, a liquid crystal display panel provided with an adjusting function which improves the visibility between one tone and another tone by changing transmission of the liquid crystal, without increasing luminance of a backlight of the liquid crystal panel is known (refer to Patent Document 1). Japanese Patent Laid-Open Publication No. 2003-186455